Printed circuit boards comprise a support structure formed from an electrically insulative material and having formed on at least one side thereof a series of electrically conductive paths or leads in the form of traces and pads. Typically, a plurality of apertures are formed through the board, and components are mounted on the board by insertion of electrically conductive pins extending from each component through the apertures. Solder connections are then formed between the conductive pins of the components and the conductive leads of the printed circuit board, thereby completing the necessary electrical connections between the various components.
As will be readily apparent, when a particular printed circuit board requires the replacement, addition, removal and/or testing of numerous components, many opportunities exist for operator error. For example, many types of components are almost identical in appearance, but widely differ in function. When the design of a particular printed circuit board requires the positioning of different types of components in relatively adjacent locations, the mounting or testing of components in incorrect locations or the removal of components from incorrect locations can usually occur. In addition, integrated circuits and other components often have a particular polarity. Even when the conductive pins of such a component are positioned in a correct aperture, the orientation of the component may be reversed, which means that the polarity of the component is incorrect.
Various systems have been proposed for component verification on printed circuit boards, such as, for example, the system and method disclosed in U.S. Pat. No. 4,469,553 issued to Robert E. Whitehead on Sep. 4, 1984. The system of the '533 Patent projects circuit board data, such as, for example, "Gerber" data from a plasma screen of a computer onto a half mirror. A printed circuit board is positioned beneath the mirror. The board can be viewed through the mirror while at the same time the "Gerber" data and component data is projected on the mirror in registry with the circuit board, so that an operator can view the circuit board through the mirror for correlating the "Gerber" data and component data projected onto the mirror with the actual circuit board positioned below the mirror.
A need has arisen for a improved system for verification of components and proper orientation of components on printed circuit boards.